Calender doctor assembly



NOV. 14, 1933. A. N RUSSELL 1,935,164

CALENDER DOCTOR ASSEMBLY Filed Jan. 9, 1951 s Sheets-Sheet 1 IlllllIlllll 0 III,

in c 45 4e 13, I

- IN VEN T0 R J AN D REWJiRUsS ELL F IG- A'JSTOFLNEY Nov. 14, 1933. NRUSSELL 1,935,164

' CALENDER DOCTOR ASSEMBLY I Filed Jan. 9, 1931 3 Sheets-Sheet 2 INVENTOR AN DREWN-BUSSELL ATTORNEY Nov. 14, 1933. A. N. RUSSELL CALENDERDOCTOR AS SEMBLY 3 Sheets-Sheet 3 Filed Jan. 9, 1931 INVENTCBRANDREWN-RUSSELL NEY Patented .Nov. 14, 1933 UNITED STATES PATENT OFFIEAndrew N. Russell, Montreal, Quebec, Canada, assignor to DominionEngineering Works Limited, Lachine, Quebec, Canada Application January9, 1931. Serial No. 501,659

21 Claims.

This invention relates to a doctor assembly for general use inconnection with rolls or cylinders over which a web of paper or othermaterial is passed during manufacture or treatment thereof. Morespecifically the invention aims to provide a doctor assemblyparticularly adapted for use on paper calender machines of the stackroll type.

One of the principal objects is to provide for withdrawal of the doctorsto a retracted position sufficiently remote from the rolls to eliminatethe difiiculties usually caused by wads of paper or other accumulationson the roll surfaces coming in contact with the doctor blades. To thisend the doctors are withdrawn from contact with the rolls a distancesuflicient to leave a clearance of about 4" between the roll surfacesand the operative edges of the doctor blades.

Another very important object is to provide a thin flexible doctor blademounted to have a high co-efiicient of local flexure so that the edge ofthe blade in contact with the surface to be doctored is remarkably freeto adjust itself to irregularities occurring on said surface.

A further and more specific object is to provide novel doctor mountingand controlling means whereby rectilinear movement, preferably in ahorizontal plane, is imparted to the doctors during positioning thereofwith reference to the roll surface, suitable provision being made tomaintain the doctors at all times parallel with the roll surface and theextent to which the operative edges of the doctor blades are withdrawnfrom contact with the rolls by the controlling means being predeterminedto leave a degree of clearance impossible to obtain by normal operationof any of the doctor controlling mechanisms now in use.

A still further object is to provide for individual or group operationof the doctors through the agency of a differential pressure deviceassociated with each doctor, the group operation of the doctors beingcontrolled by a single main valve common to a plurality of the pressuredevices and the individual operation of the doctors being controlled bya further valve associated with each individual pressure device.

Figure 1 is atransverse sectional view of a calender equipped with myimproved doctor assembly, this view being taken substantially along theline 1-1 of Figure 2.

Figure 2 is a side view, with a part broken away, of theassembly-appearing in Figure 1.

Figure 3 is an enlarged detail sectional view showing the manner ofmounting certain of the doctors and the fluid operated pistons assembledtherewith.

Figure 4 is a view of the. opposite side of certain of the elementsappearing in Figure 3.

Figure 5 is a fragmentary detailed sectional view taken along the line5-5 of Figure 4.

Figure 6 is a fragmentary front edge view of the doctor proper showingone method of mounting the doctor blade on the doctor body.

Figure 7 is a transverse sectional view taken substantially along theline 77 of Figure 6.

Figure 8 is a view similar to Figure 7 but showing a slightmodification.

Figure 9 is a longitudinal sectional end view taken along the line 9-9of Figure 8.

Referring more particularly to the drawings, 11 designates the frame ofa conventional calender equipped with the usual arrangement of calenderrolls 12. The present invention, as applied to this type of calender,contemplates no radical changes in the general arrangement of thedoctors with respect to the calender rolls but is chiefly concerned withcertain improvements in the construction and operation of the doctors.

According to this invention, each doctor 'includes a body 13 equippedwith a flexible doctor blade 14 attached to said body in a particularmanner hereinafter described. When the doctors are in their operativepositions, the blades 14 are arranged to engage the roll surfaces to bedoctored as shown to advantage in Figure 1.

All of the doctors are mounted for sliding movement to and from the rollsurfaces to be doctored and are also capable of vertical swingingmovement as hereinafter described. Each doctor body is swingablyconnected to a shaft 15 by means of suitable end and intermediate shaftreceiving bearings appearing at 16 and 17, the shaft being rotatable inthese bearings. The end portions of the shaft are rotatably carried in apair of slide bearings 18 arranged to slide in slotted guides 19 formingpart of the brackets 20 attached to the sides of the calender frame. Theextreme ends of the shaft 15 project beyond the slide bearings 19 andare equipped with pinions 21 meshing with short racks 22 slidablyassociated with the guides 19. The racks are adjustable through themedium of the screws 23 and co-operate with the pinions 21 to positionthe opposite ends of the shaft 15 when aligning the doctor withreference to the roll surface to be doctored. Adjustable stop screws 23aare carried by the inner ends of the guides 19 for engagement with theslide bearings 19 to limit I of the doctor about the axis aiforded bythe shaft 15, as hereinafter referred to. I

One slide bearing 18 of each doctor, is attached to the inner end of apiston rod 28 of relatively large diameter. A piston 29 fixed to theouter end of the piston rod is arranged to operate in a cylinder 30attached to the guide 19. The outer \end of each cylinder 39 (with theexception of the cylinders controlling the doctors associated with thetwo lowermost rolls of the calender) is connected to a header 31 bymeans of a branch pipe 32 equipped with a valve 33. The inner end ofeach of said cylinders is also connected to a header 34 by a valvelessbranch pipe 35. All of the headers 31 and 34 are supplied withcompressed air or other fluid under pressure from a common supply pipe36. The headers 34 are in continuous communication with the supply pipe36, but the flow of fluid from the supply pipe to the headers 31 iscontrolled by a single threeway valve appearing at 37.

Due to the large diameter of the piston rod 28, it will be evident thateach cylinder and piston is adapted to function as a differentialpressure device since fluid supplied to the outer end of the cylinderfrom the header 31 is effective to move the piston 29 towards the innerend of the cylinder against the resistance of the fluid which iscontinuously supplied to the last mentioned end of the cylinder from theheader 34. Assuming that the outer ends of all of the cylinders referredto are in open communication with the header 31, it will be evident thatthe position of the doctors controlled by the pistons operating in thesecylinders is dependent upon the position of the main control valve 37.If this valve is operated to place the headers 31 in communication withthe supply pipe 36, all of the doctors mentioned will be simultaneouslymoved in the direction of the calender roll to engage the doctor bladeswith the roll surfaces to be doctored. If the valve 37 is subsequentlyturned to place the headers 31 in communication with the exhaustconnection appearing at 38, ,all of the doctors will be simultaneouslywithdrawn from engagement with the rolls by the pressure of the fluidcontinuously supplied to the inner end of the cylinders from the headers34.

Individual or selective group operation of the doctors is also madepossible by the provision of the valves 33 controlling communicationbetween the outer ends of the cylinders 30 and the headers 31. Thesevalves are operable to place the outer ends of the respective cylindersin communication with the headers 31 or in communication with theatmosphere through the exhaust connections appearing at 33c. Hence byproper manipulation of these valves any selected doctor or any selectedgroup of doctors may be moved to or maintained in an operative or aninoperative position, irrespective or the status of the remainingdoctors. 1

With reference to the cylinders controfiing the doctors associated withthe two lowermost rolls of the calender, it will be noted that theopposite ends of each cylinder are connected to one of the headers 34 bythe branches appearing at 40 and 41. Fluid is continuously supplied tothe iheesgieg inner end of these cylinders through the branch 40, butthe flow of fluid to the outer ends of the cylinders is controlled bythe valve 42 corresponding to the valves 33 previously described. Whenthe valves 42ers positioned to permit the flow of fluid from the headers34 to the outer ends of the cylinders here referred to, the doctorscontrolled by the pistons operating in said cylinders are shifted totheir operative positions. When the valves 42 are positioned to placethe outer ends of said cylinders in communication with the atmospherethrough-the exhaust connections as, the fluid pressure supplied to theinner ends of the cylinders through the branch connections 40 becomeseffective to withdraw the doctors from engagement with theroll'surfaces.

With this explanation, it will be understood that they positioning ofthe doctors associated with the two lowermost calender rolls is manuallycontrollable by the valves 42 irrespective of the operation of the maincontrol valve 37 previously referred to.

As previously pointed out only one slide bearing 18 of each doctor isconnected to the operating piston of the associated pressure device and,hence, it is desirable that some means be provided for causing the endsof the doctor to move in unison so as. to maintain the doctor at alltimes parallel with the roll surface to be doctored. This isaccomplished in the present instance by the pinions 21 on the shaft 15co-operating with the racks 22in the following manner. Movement of thepiston operated slide bearing 18 in its guide 19 causes. the adjacentpinion 21 to be rotated as it. is moved relative to the co-operatingrack 22. The rotation thus imparted to the shaft 15 causes pinion 21 atthe opposite end of the shaft to travel over the rack 22 so that theshaft and the doctor associated therewith is at all times parallel tothe roll surface to be doctored. During movement of the doctor to itsoperative position the doctor blade 14 is brought into engagement withthe roll surface before the movement of the slide bearings 18 isarrested by engagement with the stop screws 23a. Hence, as the slidebearings 18 continue their forward movement into engagement with thescrews 23a, the doctors are caused to swing upwardly about the shaft 15so that, in its final operative position, each. doctor is held to theroll surface solely by its own weight. i

when the blade 1.14 is withdrawn from engagement with the roll thedoctor then swings about the shaft 15in the opposite direction untilfurther swinging movement in this direction is arrested by engagement ofthe lugs 25 and 26. The permissable travel of the slide bearings 18 inthe guides 19 is such that, in the retracted position of the doctors, aclearance of approximately 4 inches is left between the roll surfacesand the operative edges of the doctor blades 14. This clearance isconsiderably in excess of that prothat the heel portion of thedoctorblade is confined between the doctor body 13 and a cover plate 45 and isprovided with positioning pins 46 entering suitable sockets 47 providedin the doctor body. The cover plate is provided with a groove 48 inwhich is arranged a metal strip 49 carrying a plurality of relativelyspaced bowed springs 50. The arrangement is such that the ends of eachspring bear resiliently upon the heel portion of the doctor bladeimmediately in line with the positioning pins 46. The advantage of thisarrangement is that it permits-the free edge of the doctor blade toaccommodate itself to any accumulations or irregularitiesoccurring onthe roll surface with which the plate is engaged.

In Figures 8 and 9 I have shown a modified form of blade mounting inwhich the strip 49 and springs 50 are replaced by a strip 52 composed ofsoft rubber or similar material. The lower .face of the strip 52 isnotched to provide a series of partially separated portions 53 whichbear resiliently on the heel portion of the doctor blade and serve thepurpose of the bowed springs 50 previously described.

Having thus described my invention, what I claim is:--

l; A doctor mounted to slide into and out of engagement with the surfaceto be doctored, a doctor positioning mechanism connected to one end ofthe doctor, and means for causing both ends of the doctor to move inunison to maintain the doctor at all times parallel with the doctoredsurface.

2. A doctor equipped with a shaft rotatably connected therewith, slidebearings rotatably carrying said shaft, pinions fixed to the ends ofsaid shaft, stationary racks meshing with said pinions and meansconnected to one of said slide bearings to impart sliding movementthereto.

3. A doctor equipped with a shaft rotatably connected thereto, slidebearings rotatably carrying said shaft, brackets supporting said bearingfor sliding movement, racks carried by said brackets, and pinions on theshaft meshing with said racks.

4. A doctor equipped with a shaft rotatably connected thereto, slidebearings rotatably mounting said shaft, guides supporting said slidebearings, racks adjustably carried by said guides, pinions on said shaftmeshing with said racks and means connected to one of said slidebearings to impart sliding movement thereto.

5. The combination with a plurality of doctors of a differentialpressure device attached to each doctor to control the positioning ofthe doctor with respect to the surface to be doctored, and means forcontrolling the flow of fluid to and from said pressure devices saidmeans including valves operable to effect selective individual or groupoperation of the doctors.

6. The combination with a plurality of doctors of a differentialpressure device, attached to each doctor for controlling the positioningof the doctor with respect to the surface to be doctored, each deviceincluding a cylinder and a piston means operating in said cylinder andconnected to one of said doctors, a fluid supply pipe header receivingfluid from a supply pipe, branch connections for placing certain of theheaders in communication with one end of said cylinders, branchconnections for placing the remaining headers in communication with theremaining ends of said cylinders, a single valve controlling the passageof fluid from the supply pipe to the headers connected to one end ofsaid cylinder and additional valves arranged in the branch connectionsbetween the cylinders and the last mentioned headers.

7. The combination with a plurality of doctors of a difi'erentialpressure device attached to each doctor for controlling the positioningof the doctor with respect to the surface to be doctored, means forsupplying motive fluid to said devices, and means for controlling thesupply of motive fluid to effect simultaneous operation of the pressuredevices connected to all of said doctors or to operate merely thepressure devices controlling one or more selected doctors withoutaffecting the position of the remaining doctors.

8. The combination with a doctor movable to and from a surface to bedoctored of a differential pressure device includinga cylinder andpiston means operating in said cylinder and connected to one end of thedoctor, means for continuously supplying fluid to one end-of eachcylinder to create a pressure tending to withdraw the doctor Ifrom-engagement with said surface, and means for supplying fluid to theremaining end of each cylinder to create r pressure sufficient toovercome the first mentioned pressure and to move the doctor intoengagement with said surface said last means including manually operablevalves for placing the last mentioned ends of the cylinder incommunication with the atmosphere or with the source of fluid pressure.

9. The combination of a doctor including a shaft rotatably connected tothe doctor body, slide bearings rotatably mounting said shaft, guidesslidably supporting said bearings and means for moving the bearings insaid guides to shift the doctor towards and away from the surface to bedoctored.

10. The combination of a doctor including a shaft, rotatably connectedto the doctor body, slide bearings rotatably mounting said shaft guidesslidably supporting said bearings, racks carried by said guides, pinionsfixed to said shaft and\meshing with said racks and doctor positioningmeans connected to one of the bearings.

11. The combination of a doctor including a body, a shaft rotatablyattached to the body and projecting beyond the ends thereof, slidebearings rotatably receiving the ends of said shaft, guides slidablysupporting said bearings, co-acting stop members carried by the bearingsand the doctor to limit tilting movement of the doctor in one direction,racks carried by said guides, pinions fixed to said shaft and meshingwith said racks and means connected to one of said bearings to advanceor retard the doctor with reference to the surface to be doctored.

12. A doctor comprising a body, a cover member secured thereto, a doctorblade having aportion thereof interposed between the body and the covermember and provided with positioning pins received in sockets formed insaid body and resilient pressure applying means interposed between theblade and the cover member.

13. A doctor assembly including a pair of slide bearings movable to andfrom the surface to be doctored, a shaft having its ends mounted in saidbearings, a doctor pivotally suspended from said shaft and adjustablemeans for limiting pivotal movement of the doctor in one direction.

14. A doctor assembly including a pair of slide bearings movable to andfrom the surface to be doctored, a shaft having its ends mounted in saidbearings, a doctor pivotally suspended from said shaft and coacting stopmembers'carried by the doctor and one of said bearings for holding thedoctor in a definite position and for limiting piv- 1 6. A doctorassembly including a pair of slide bearings mounted to slide toward andaway from the surface to be doctored, a doctor body pivotally carriedbetween said bearings, a cover member secured to said body, a thinflexible doctor blade having its heel portion interposed between thebddy and the cover member and resilient pressure applying means arrangedbeneath the cover and bearing on the upper surface of the blade.

1'7. A doctor comprising a body, a cover member secured to said body, adoctor blade having its heel portion interposed between the body and thecover member so that the body constitutes a fulcrum about which theblade is movable in the manner of an intermediately pivoted lever whenthe scraping edge of the blade; is pressed against the surface to bedoctored, the movement of the heel portion of the blade being in thedirection of the cover member and the movement of the projecting portionof the blade being in the opposite direction, and resilient pressureapplying means interposed between the heel portion of the blade and theopposing surface of the cover member towards which this portion of theblade is movable as aforesaid.

18. A doctor comprising a body, a cover memshaft, stationary racks bersecured to said a portion interposed between the body and the covermember and a plurality of bowed springs interposed between the heelportion of the blade and the cover member and lying at the side of theheel portion opposite that engaged with the body.

19. A doctor comprising a body, a cover member secured thereto, a doctorblade having a portion thereof interposed between the body and the covermember, and a series of bowed springs interposed between the covermember and the blade with the ends of the springs bearing on the blade.

20. A doctor comprising a body, a cover member secured thereto, a doctorblade having a portion thereofinterposed between the body and the covermember, a series of bowed springs interposed between the cover memberand the blade with the opposite ends of each spring bearing on the bladeand a common connecting strip secured to the intermediate portions ofsaid springs. v

21. A doctor comprising a body, a cover member secured to said body andhaving a groove formed in its body opposing surface, a doctor bladehaving a portion thereof interposed between the body and the covermember and flatly engaging said body, a metal strip arranged in saidgroove and a plurality of relatively spaced bowed springs carried bysaid strip with the ends of each spring bearing on the doctor blade.

I ANDREW N. RUSSELL.

doctor havin its heel

